For the reasons that in a heat treatment device for synthetic fiber filament yarns of this kind which utilizes characteristics of saturated steam of heat medium liquid, the heat medium liquid condensed during heat treatment is returned to a boiler for heating the heat medium liquid without accumulating it inside hot pins, the heat treatment device cannot be mounted to a bottom surface of a laterally extended closed container in such a fashion as to protrude downwardly. Therefore, the heat treatment device is mounted to a side surface so as to protrude sidewardly. So, when the heat treatment device is installed above a separate vertically extended hot plate which is longer in vertical direction, the overall height of a setup comprising the heat treatment device and the hot plate increases, as a result it becomes difficult to secure a building in which the setup can be installed.
Such a tendency is remarkable particularly when the length of the vertically extended hot plate is lengthened with the increase of a feeding speed of the filament yarns.
In the heat treatment device for synthetic fiber filament yarns which utilizes characteristics of saturated steam of the heat medium liquid via the heating surface of the hot pins as described above, it is an object of the present invention to reduce the overall height of the setup comprising the heat treatment device and the hot pins by making it possible to arrange the heat treatment device on the same plane with the laterally extended hot plate instead of arranging the heat treatment device above the vertically extended hot plate so that a building for installing the setup therein can be easily secured.